Wireless communications relying on Unmanned
Aerial Vehicles (UAVs) is a promising candidate in future
communication systems. Compared with conventional terrestrial
communications, UAV networks has some significant benefits
including cost-effectiveness, mobility, fast deployment, higher
probability of Line-of-Sight (LoS) links between UAV and
ground terminals. Based on ideal conditions of high Signal-to-
Noise Ratio (SNR), Non-Orthogonal Multiple Access (NOMA)
with fixed power allocation factor is adopted to indicate
performance of two users. These ground user from UAV is
independent of channel and trajectory parameters is further
evaluated under impact of imperfect channel state information
(CSI). We drive the closed-form formula of outage probability
for two ground users. Simulation results provide impacts of
system parameters on outage behavior.